Hot gas defrost system for refrigeration systems

Abstract

The invention provides a full flow vaporizing accumulator for use in a refrigeration system employing hot gas from the compressor to periodically defrost the cooling coil, or coils where multiple coils are employed. The hot gas cooled in the defrosting coil produces liquid refrigerant droplets that may damage the expensive compressor. The device replaces the usual accumulator that is always provided to try to ensure that these droplets do not reach the compressor. The interior of the vaporizing accumulator is divided by a partition into two chambers, one of which the cooled gas from the defrosting coil is delivered via a perforated tube having one end blocked, so that the fluid is directed forcefully radially outward to make it turbulent. The interiors of the two chambers are connected by a plurality of fine bores in the partition, which discharge the turbulent fluid into intimate contact with a coil heated by the hot gas that is fed thereto before it is fed to the cooling coil to defrost it. The outlet from the second chamber consists of the usual J-shaped accumulator outlet tube having a drain hold at its lowest point. An orifice or restriction is provided at the outlet for the hot gas from the heated coil and increases the back-pressure applied to the compressor by an amount of between 20% and 70%, preferably by between 40% and 60%, rendering the device self-balancing to prevent compressor overload.

I claim: 
     
       1. A liquid refrigerant vaporising accumulator for use in a refrigeration system employing a compressor and hot refrigerant fluid from the compressor to defrost a coil or coils thereof, the vaporizing accumulator comprising: a body member;   a partition member within the interior of the body member and dividing the interior into first and second chambers;   an inlet to the first chamber for connection into the refrigeration system so as to receive the refrigerant fluid exiting from the coil under defrost and to produce turbulence therein as it enters the first chamber;   a plurality of bores in the partition connecting the interiors of the two chambers, constituting the only outlet for all of the refrigerant fluid from the first chamber, and for the passage of the turbulent refrigerant fluid from the first chamber to the second chamber;   a heat exchange pipe of heat conductive material disposed in the second chamber adjacent the said plurality of bores for its surface to be impinged by the turbulent refrigerant fluid passing through the bores for vaporization of any liquid refrigerant entrained therein;   an inlet to the heat exchange pipe and an outlet therefrom for connection into the refrigeration system to receive and to deliver respectively hot refrigerant fluid received from the compressor; and   an outlet from the second chamber for all of the refrigerant fluid into an accumulator outlet pipe within the second chamber.   
     
     
       2. A vaporizing accumulator as claimed in claim 1, wherein the body member is cylindrical and in operation is disposed with its longitudinal axis vertical; the partition member is a transverse circular partition dividing the interior of the body member into a first upper chamber and a second lower chamber;   the plurality of bores is disposed in the partition circumferentially thereof to be close to the inner wall of the body member; and   the heat exchange pipe has the form of a helical coil mounted in the second chamber adjacent its inner wall immediately beneath the bores to be impinged by refrigerant fluid passing therethrough.   
     
     
       3. A vaporizing accumulator as claimed in claim 2, and including a cylindrical baffle of smaller diameter than the body member, disposed within the second chamber to form between itself and the inner wall of the body member an annular space receiving the heat exchange pipe helical coil and confining the flow of the refrigerant fluid onto the coil. 
     
     
       4. A vaporizing accumulator as claimed in claim 1, wherein the inlet to the first chamber producing said turbulence of the entering refrigerant fluid comprises an inlet pipe extending across the chamber, the wall of the inlet pipe being provided with a plurality of bores directing the refrigerant fluid passing therein radially outwards therefrom to impinge against the adjacent chamber walls and thereby become turbulent before its passage through the bores in the partition member. 
     
     
       5. A vaporizing accumulator as claimed in claim 1, wherein the accumulator outlet pipe is of J-shape with its inlet to the second chamber close to the partition member to be above the level of any liquid in the second chamber. 
     
     
       6. A vaporizing accumulator as claimed in claim 1, wherein the total flow area provided by all of the bores in the partition is not more than 1.5 times the cross-sectional flow area of the inlet to the first chamber. 
     
     
       7. A vaporizing accumulator as claimed in claim 6, wherein the total flow area provided by all of the said bores is between 0.9 and 1.2 times the cross-sectional flow area. 
     
     
       8. A vaporizing accumulator as claimed in claim 1 and including a refrigerant fluid flow restriction at or connected to the heat exchange pipe outlet for producing an increase in back pressure of the refrigerant fluid in the pipe. 
     
     
       9. A vaporizing accumulator as claimed in claim 8, wherein the increase in back pressure produced by the fluid flow restriction is between 20% and 70% of the pressure in the absence of the fluid flow restriction. 
     
     
       10. A vaporizing accumulator as claimed in claim 9, wherein the increase in back pressure produced by the fluid flow restriction is between 40% and 60% of the pressure in the absence of the fluid flow restriction. 
     
     
       11. A vaporizing accumulator as claimed in claim 8, wherein the fluid flow restrictor is directly attached to the pipe outlet. 
     
     
       12. A vaporizing accumulator as claimed in claim 1, wherein the said bores in the partition are of flow area from 8 to 18 sq.mm (0.012 to 0.028 sq.in) and the total flow area of all of the bores is adjusted by adjustment of the number of bores. 
     
     
       13. A vaporizing accumulator as claimed in claim 8, wherein a portion of pipe of increased flow capacity is provided downstream of the fluid flow restriction to provide for re-evaporation of any liquid in the hot gas passing through the restriction. 
     
     
       14. A hot refrigerant fluid defrost system for use in a refrigeration system for defrost of a coil or coils thereof, the system comprising: a controllable flow valve adapted for connection to the outlet of a compressor pump to receive hot compressed refrigerant fluid therefrom;   a coil to be defrosted having an inlet and an outlet; and   a vaporizing accumulator connected to the coil for vaporizing liquid fluid issuing from the coil outlet to prevent its delivery to the compressor inlet, the vaporizing accumulator comprising:   a body member;   a partition member within the interior of the body member and dividing the interior into first and second chambers;   an inlet to the first chamber for connection into the refrigeration system so as to receive the refrigerant fluid exiting from the coil under defrost and to produce turbulence therein as it enters the first chamber;   a plurality of bores in the partition connecting the interiors of the two chambers, constituting the only outlet for all of the refrigerant fluid from the first chamber, and for the passage of the turbulent refrigerant fluid from the first chamber to the second chamber;   a heat exchange pipe of heat conductive material disposed in the second chamber adjacent the said plurality of bores for its surface to be impinged by the turbulent refrigerant fluid passing through the bores for vaporization of any liquid refrigerant entrained therein;   an inlet to the heat exchange pipe and an outlet therefrom for connection into the refrigeration system to receive and to deliver respectively hot refrigerant fluid received from the compressor; and   an outlet from the second chamber for all of the refrigerant fluid into an accumulator outlet pipe within the second chamber.   
     
     
       15. A system as claimed in claim 14, wherein the body member is cylindrical and in operation is disposed with its longitudinal axis vertical; the partition member is a transverse circular partition dividing the interior of the body member into a first upper chamber and a second lower chamber;   the plurality of bores is disposed in the partition circumferentially thereof to be close to the inner wall of the body member; and   the heat exchange pipe has the form of a helical coil mounted in the second chamber adjacent its inner wall immediately beneath the bores to be impinged by refrigerant fluid passing therethrough.   
     
     
       16. A system as claimed in claim 15, and including a cylindrical baffle of smaller diameter than the body member, disposed within the second chamber to form between itself and the inner wall of the body member an annular space receiving the heat exchange pipe helical coil and confining the flow of the refrigerant fluid onto the coil. 
     
     
       17. A system as claimed in claim 14, wherein the inlet to the first chamber producing said turbulence of the entering refrigerant comprises an inlet pipe extending across the chamber, the wall of the inlet pipe being provided with a plurality of bores directing the refrigerant fluid passing therein radially outwards therefrom to impinge against the adjacent chamber walls and thereby become turbulent before its passage through the bores in the partition member. 
     
     
       18. A system as claimed in claim 14, wherein the accumulator outlet pipe is of J-shape with its inlet to the second chamber close to the partition member to be above the level of any liquid in the second chamber. 
     
     
       19. A system as claimed in claim 14, wherein the total flow area provided by all of the bores in the partition is not more than 1.5 times the cross-sectional flow area of the inlet to the first chamber. 
     
     
       20. A system as claimed in claim 19, wherein the total flow area provided by all of the said bores is between 0.9 and 1.2 times the cross-sectional flow area. 
     
     
       21. A system as claimed in claim 14, and including a refrigerant fluid flow restriction at or connected to the heat exchange pipe outlet for producing an increase in back pressure of the refrigerant fluid in the pipe. 
     
     
       22. A system as claimed in claim 21, wherein the increase in back pressure produced by the fluid flow restriction is between 20% and 70% of the pressure in the absence of the fluid flow restriction. 
     
     
       23. A system as claimed in claim 22, wherein the increase in back pressure produced by the fluid flow restriction is between 40% and 60% of the pressure in the absence of the fluid flow restriction. 
     
     
       24. A system as claimed in claim 22, wherein the fluid flow restrictor is directly attached to the pipe outlet. 
     
     
       25. A system as claimed in claim 14, wherein the said bores in the partition are of flow area from 8 to 18 sq.mm (0.012 to 0.028 sq.in.) and the total flow area of all of the bores is adjusted by adjustment of the number of bores. 
     
     
       26. A system as claimed in claim 22, wherein a portion of pipe of increased flow capacity is provided downstream of the fluid flow restriction to provide for re-evaporation of any liquid in the hot gas passing through the restriction. 
     
     
       27. A system as claimed in claim 14, wherein the refrigeration system is incorporated in a heat pump. 
     
     
       28. A system as claimed in claim 14, and comprising a plurality of coils to be defrosted, wherein there is provided a single vaporizing accumulator connected to all of the coil outlets to receive refrigerant therefrom. 
     
     
       29. A refrigeration system comprising: a refrigerant compressor;   a cooling coil having an inlet and an outlet;   an expansion device for expanding and cooling refrigerant connected between the compressor and the cooling coil inlet;   a controllable defrost control valve connected to the compressor outlet to receive hot compressed refrigerant fluid therefrom;   and a liquid refrigerant vaporizing accumulator connected to the coil for vaporizing liquid fluid issuing from the coil outlet to prevent its delivery to the compressor inlet, the vaporizing accumulator comprising:   a body member,   a partition member within the interior of the body member and dividing the interior into first and second chambers;   an inlet to the first chamber for connection into the refrigeration system so as to receive the refrigerant fluid exiting from the coil under defrost and to produce turbulence therein as it enters the first chamber;   a plurality of bores in the partition connecting the interiors of the two chambers, constituting the only outlet for all of the refrigerant fluid rom the first chamber, and for the passage of the turbulent refrigerant fluid from the first chamber to the second chamber;   a heat exchange pipe of heat conductive material disposed in the second chamber adjacent the said plurality of bores for its surface to be impinged by the turbulent refrigerant fluid passing through the bores for vaporization of any liquid refrigerant entrained therein;   an inlet to the heat exchange pipe and an outlet therefrom for connection into the refrigeration system to receive and to deliver respectively hot refrigerant fluid received from the compressor; and   an outlet from the second chamber for all of the refrigerant fluid into an accumulator outlet pipe within the second chamber.   
     
     
       30. A system as claimed in claim 29, wherein the body member is cylindrical and in operation is disposed with its longitudinal axis vertical; the partition member is a transverse circular partition dividing the interior of the body member into a first upper chamber and a second lower chamber;   the plurality of bores is disposed in the partition circumferentially thereof to be close to the inner wall of the body member; and   the heat exchange pipe has the form of a helical coil mounted in the second chamber adjacent its inner wall immediately beneath the bores to be impinged by refrigerant fluid passing therethrough.   
     
     
       31. A system as claimed in claim 30, and including a cylindrical baffle of smaller diameter than the body member, disposed within the second chamber to form between itself and the inner wall of the body member an annular space receiving the heat exchange pipe helical coil and confining the flow of the refrigerant fluid onto the coil. 
     
     
       32. A system as claimed in claim 29, wherein the inlet to the first chamber producing said turbulence of the entering refrigerant fluid comprises an inlet pipe extending across the chamber, the wall of the inlet pipe being provided with a plurality of bores directing the refrigerant fluid passing therein radially outwards therefrom to impinge against the adjacent chamber walls and thereby become turbulent before its passage through the bores in the partition member. 
     
     
       33. A system as claimed in the accumulator outlet pipe is of J-shape with its inlet to the second chamber close to the partition member to be above the level of any liquid in the second chamber. 
     
     
       34. A system as claimed in claim 29, wherein the total flow area provided by all of the bores in the partition is not more than 1.5 times the cross-sectional flow area of the inlet to the first chamber. 
     
     
       35. A system as claimed in claim 34, wherein the total flow area provided by all of the said bores is between 0.9 and 1.2 times the cross-sectional flow area. 
     
     
       36. A system as claimed in claim 29, and including a refrigerant fluid flow restriction at or connected to the heat exchange pipe outlet for producing an increase in back pressure of the refrigerant fluid in the pipe. 
     
     
       37. A system as claimed in claim 36, wherein the increase in back pressure produced by the fluid flow restriction is between 20% and 70% of the pressure in the absence of the fluid flow restriction. 
     
     
       38. A system as claimed in claim 37, wherein the increase in back pressure produced by the fluid flow restriction is between 40% and 60% of the pressure in the absence of the fluid flow restriction. 
     
     
       39. A system as claimed in claim 37, wherein the fluid flow restrictor is directly attached to the pipe outlet. 
     
     
       40. A system as claimed in claim 29, wherein the said bores in the partition are of flow area from 8 to 18 sq.mm (0.012 to 0.028 sq.in.) and the total flow area of all of the bores adjusted by adjustment of the number of bores. 
     
     
       41. A system as claimed in claim 37, wherein a portion of pipe of increased flow capacity is provided downstream of the fluid flow restriction to provide for re-evaporation of any liquid in the hot gas passing through the restriction. 
     
     
       42. A system as claimed in claim 29, wherein the refrigeration system is incorporated in a heat pump. 
     
     
       43. A system as claimed in claim 29, and comprising a plurality of coils to be defrosted, wherein there is provided a single vaporizing accumulator connected to all of the coil outlets to receive refrigerant therefrom.